The invention pertains to a casting/rolling installation for producing hot-rolled strip. In addition, the invention pertains to a method for removing and installing rolls in a reducing stand of the casting/rolling installation.
Casting/rolling installations for casting and rolling metal strip are generally known from the prior art. A known type of such a casting/rolling installation is, for example, the so-called “compact strip production” installation. This known type of installation is shown in FIG. 4 and is described below in schematic terms. Additional types of installations are also possible, which means that the example is not to be understood as limiting in any way.
FIG. 4 shows a single-strand casting/rolling installation 100. In it, liquid metal, typically liquid steel, is transported in a tundish 180 by means of a casting bay crane 190 to a distributor device 120, typically a so-called swiveling tundish. From the distributor device 120, the liquid steel is conducted into a first mold 112-1, where it solidifies on the cooled edges of the mold, as a result of which a strand shell is formed. At the outlet of the mold 112-1, the cast strand, which is still liquid on the inside, is sent to a downline roller apron 114-1, which deflects the cast strand emerging vertically from the mold 112-1 into a horizontal plane. As it is being guided along the roller apron 114-1, the cast strand is cooled further until it has completely solidified. After its complete solidification, the cast strand 210-1 passes through a first reducing stand 116-1, which rolls the cast strand and thus reduces its thickness. Seen in the casting direction R, the cast strand then passes through a shears 192, which cuts the strand into slabs 220-1. The shears 192 are typically assigned a scrap box 193 for carrying away the metal scrap which accumulates during the cutting of the cast strand. The shears are also typically followed by a tunnel furnace 194 to hold the slabs at temperature or to increase the temperature of the slabs slightly to the slab rolling temperature required by the following finishing line 195. In the finishing line, the slabs are rolled out into hot-rolled strip 230-1. Downstream from the finishing line 195, a cooling section 196 and a reel device 197 are typically provided, the latter being used to wind up the cooled hot-rolled strip.
In addition to the single-strand installation just described with reference to FIG. 4, multi-strand installations are also known, in which several of the strands shown in FIG. 4 are arranged parallel to each other.
The casting/rolling installation just described with reference to FIG. 4 takes advantage of the heat of casting, which significantly decreases the need to reheat the slabs in the tunnel furnace 194 in comparison with the method of supplying slabs which have already cooled.
For metallurgical reasons, it is favorable to achieve a degree of deformation of the cast strand 210-1 of at least 60-80% from the outlet of the roller apron to the reel device 197, where the hot strip is coiled up. During the production of the thicker grades of hot-rolled strip, slab thicknesses in the range of 40-120 mm are reached. In the case of thicker slabs or thicker hot-rolled strip, it is advantageous for the deformation process to be conducted in several stages. For this purpose, the cast strand is subjected in the previously mentioned reducing stand 116-1 to a first deformation step as soon as it leaves the roller apron 114-1 and thus brought to a thickness which is suitable for the following compact finishing line 195, where the slabs are brought to their final, desired thickness.
From an energy standpoint, it is logical to conduct the first deformation step immediately after casting. To realize this, the first reducing stand 116-1 is set up directly behind the outlet of the roller apron 114-1 and thus under the casting platform 118-1 of the casting/rolling installations 100. The casting platform, as shown in FIG. 4, is typically set up as a horizontal work platform at the level of the mold 112-1. On the casting platform, teams of operators must perform maintenance jobs in particular on the distribution device 120, and tools and consumable materials are also stored on the casting platform. For reasons of occupational safety, the casting platform is configured as a closed but easily walkable work zone. The entire casting installation is operated by one person from a control stand 198, which, as shown by way of example in FIG. 4, is arranged above the casting platform.
The arrangement of the first reducing stand 116-1 directly after the roller apron and underneath the casting platform 118-1 just described as being advantageous with respect to energy use suffers from the disadvantage that the casting bay crane 190 traveling above the casting platform 118-1 cannot access the reducing stand 116-1. In particular, the casting bay crane 190 therefore cannot be used to change the rolls 310, 320-1, 320-2 of the reducing stand 116-1. This is also true for the reason that the operator in the control. stand 198, from which the movement of the casting bay crane 190 is controlled, has no view of the area where the reducing stand 116-1 is installed, because this view is blocked by the casting platform 118-1.
It must also be taken into account that the operating teams on the casting platform and the operating teams underneath the casting platform in the area of the outlet from the roller apron typically have neither visual nor spoken contact with each other, so that work being carried out in parallel by the two teams can lead under certain circumstances to hazardous situations.
One possible way of changing the rolls in the reducing stand 116-1 underneath the casting platform 118-1 could consist in providing a separate crane underneath the casting platform. Such a crane, however, would require considerable investment, and in addition the height of the installation or of the casting platform may not always be sufficient to allow the crane to be operated there usefully. The need to elevate the casting platform in these cases would also necessarily be associated with considerable cost.
In the prior art, there is a wide variety of known roll-changing devices for removing and carrying away worn-out rolls from a reducing stand and for bringing up and installing new rolls in the stand. Among others, roll-changing devices in the form of a turntables are also known. Such turntables are known specifically from, for example, German Offenlegungsschrift No. DE 1 527 622; German Patent No. 851941; and Patent DE 693 224, published by the Patent Office of the German Reich. The last-mentioned patent discloses a rotating table, which can be turned by a drive. A track for accepting sets of rolls is arranged on the turntable. At the periphery of the turntable, there is typically an intermediate holding station for the rolls, which comprises track spurs, arranged in a star-like manner, connecting to the track on the turntable. A device is provided on the turntable to push a set of rolls from the intermediate holding station onto or up to the turntable and vice versa to push a set of rolls off the turntable and onto the holding station. The track spurs on the holding station allow individual rolls or a complete set of rolls, after they have been removed from the roll stand, to be deposited on a track spur and for a second set to be moved into position immediately in the roll stand without the need for a crane. The same device, which can be operated hydraulically, for example, is also adapted to bring new rolls into position opposite the roll stand and then to push the rolls into the stand and vice versa to pull worn-out rolls back out of the stand.
U.S. Pat. No. 1,833,376, furthermore, discloses a roll-changing device in the form of a turntable, which can be locked in certain rotational positions and thus prevented from rotating further.